fs: prevent page refcount overflow in pipe_buf_get

commit 15fab63e1e57be9fdb5eec1bbc5916e9825e9acb upstream.

Change pipe_buf_get() to return a bool indicating whether it succeeded
in raising the refcount of the page (if the thing in the pipe is a page).
This removes another mechanism for overflowing the page refcount.  All
callers converted to handle a failure.

Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index baaed4d..249de20 100644 (file)
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1989,10 +1989,8 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
                rem += pipe->bufs[(pipe->curbuf + idx) & (pipe->buffers - 1)].len;
 
        ret = -EINVAL;
-       if (rem < len) {
-               pipe_unlock(pipe);
-               goto out;
-       }
+       if (rem < len)
+               goto out_free;
 
        rem = len;
        while (rem) {
@@ -2010,7 +2008,9 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
                        pipe->nrbufs--;
                } else {
-                       pipe_buf_get(pipe, ibuf);
+                       if (!pipe_buf_get(pipe, ibuf))
+                               goto out_free;
+
                        *obuf = *ibuf;
                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
                        obuf->len = rem;
@@ -2033,11 +2033,11 @@ static ssize_t fuse_dev_splice_write(struct pipe_inode_info *pipe,
        ret = fuse_dev_do_write(fud, &cs, len);
 
        pipe_lock(pipe);
+out_free:
        for (idx = 0; idx < nbuf; idx++)
                pipe_buf_release(pipe, &bufs[idx]);
        pipe_unlock(pipe);
 
-out:
        kvfree(bufs);
        return ret;
 }

diff --git a/fs/pipe.c b/fs/pipe.c
index c51750e..2a297bc 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -189,9 +189,9 @@ EXPORT_SYMBOL(generic_pipe_buf_steal);
  *     in the tee() system call, when we duplicate the buffers in one
  *     pipe into another.
  */
-void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
+bool generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 {
-       get_page(buf->page);
+       return try_get_page(buf->page);
 }
 EXPORT_SYMBOL(generic_pipe_buf_get);
 

diff --git a/fs/splice.c b/fs/splice.c
index c78e0e3..485e409 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1584,7 +1584,11 @@ retry:
                         * Get a reference to this pipe buffer,
                         * so we can copy the contents over.
                         */
-                       pipe_buf_get(ipipe, ibuf);
+                       if (!pipe_buf_get(ipipe, ibuf)) {
+                               if (ret == 0)
+                                       ret = -EFAULT;
+                               break;
+                       }
                        *obuf = *ibuf;
 
                        /*
@@ -1658,7 +1662,11 @@ static int link_pipe(struct pipe_inode_info *ipipe,
                 * Get a reference to this pipe buffer,
                 * so we can copy the contents over.
                 */
-               pipe_buf_get(ipipe, ibuf);
+               if (!pipe_buf_get(ipipe, ibuf)) {
+                       if (ret == 0)
+                               ret = -EFAULT;
+                       break;
+               }
 
                obuf = opipe->bufs + nbuf;
                *obuf = *ibuf;

diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 66ee63c..7897a3c 100644 (file)
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -108,18 +108,20 @@ struct pipe_buf_operations {
        /*
         * Get a reference to the pipe buffer.
         */
-       void (*get)(struct pipe_inode_info *, struct pipe_buffer *);
+       bool (*get)(struct pipe_inode_info *, struct pipe_buffer *);
 };
 
 /**
  * pipe_buf_get - get a reference to a pipe_buffer
  * @pipe:      the pipe that the buffer belongs to
  * @buf:       the buffer to get a reference to
+ *
+ * Return: %true if the reference was successfully obtained.
  */
-static inline void pipe_buf_get(struct pipe_inode_info *pipe,
+static inline __must_check bool pipe_buf_get(struct pipe_inode_info *pipe,
                                struct pipe_buffer *buf)
 {
-       buf->ops->get(pipe, buf);
+       return buf->ops->get(pipe, buf);
 }
 
 /**
@@ -178,7 +180,7 @@ struct pipe_inode_info *alloc_pipe_info(void);
 void free_pipe_info(struct pipe_inode_info *);
 
 /* Generic pipe buffer ops functions */
-void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
+bool generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
 int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 5455ee0..1bd7a75 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6823,12 +6823,16 @@ static void buffer_pipe_buf_release(struct pipe_inode_info *pipe,
        buf->private = 0;
 }
 
-static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
+static bool buffer_pipe_buf_get(struct pipe_inode_info *pipe,
                                struct pipe_buffer *buf)
 {
        struct buffer_ref *ref = (struct buffer_ref *)buf->private;
 
+       if (refcount_read(&ref->refcount) > INT_MAX/2)
+               return false;
+
        refcount_inc(&ref->refcount);
+       return true;
 }
 
 /* Pipe buffer operations for a buffer. */